Randall d knight 대학물리학 솔루션 - randall d knight daehagmullihag sollusyeon

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32-1

Conceptual Questions

32.1. (a) a: –100 V b: +60 V c: +80 V. The emf is the x-component of the counterclockwise rotating vectors.

(b) a: Decreasing b: Decreasing c: Increasing

32.2. (a) 1.0 A. Use /.

RR

IVR= (b) 4.0 A. Use 0

//.

RR

IVRR

ε

== (c) 2.0 A. R

I does not depend on frequency.

32.3. (a) 4.0 A. Use 0c

IC

ωε

= for all parts of this question. (b) 4.0 A (c) 4.0 A

32.4. (a) 100 Hz.

c

f= Use 1

2.

cc

f

C

ωπ

== (b) 100 Hz. Use 1

2.

cc

f

C

ωπ

== (c) 200 Hz. The crossover

frequency does not depend on the peak emf.

32.5. (a) 1.0 A.

L

I= Use 0

//()

LLL

IVXL

εω

== for all parts of this question. (b) 4.0 A.

L

I=(c) 1.0 A.

L

I=

32.6. (a) 1000 Hz. Use 0

1.

C

ω

= Resistance does not matter. (b) 11000Hz707.1Hz

2=

(c) 11000Hz707.1Hz

2= (d) 1000 Hz. Peak emf does not matter.

32.7. Less than. Here the current leads the emf, so we know that

φ

< 0 (see Equation 35.22). From Equation 35.27, we find

1

tan001

LCL

LC

C

XXX

XX

RX

φ

−−

⎛⎞

=<⇒−<⇒<

⎜⎟

⎝⎠

The reactances are given by 1/()

c

XC

ω

= and ,

L

XL

ω

= and the resonance frequency is 01/.

C

ω

= Combining

these relationships gives

2

0

1

1

L

C

XLC

XLC

ωωω

=<⇒<=

32.8. We are given that 0.

ωω

< From the last relationship of the analysis in Q32.7, we see that this implies that

,

LC

XX> so

φ

> 0 and the current lags the emf.

32.9. The power will increase when the peak current I increases. This will increase when you (1) decrease R, (2) set

.

LC

XX=

ACCIRCUITS 32